This book asserts that teacher development should remain the primary medium for school improvement. It aims to reinvigorate research into teacher development by focusing attention on theoretical areas that were implied but not fully developed during the last century. Jonathan Neufeld builds on the work of many well known writers such as Michael Fullan, Andy Hargreaves and David Labaree and argues that developing teachers was the promising path to educational reform. The author shows clearly what conceptual and philosophical foundations appealed to researchers during the early, middle, and later stages of this movement to develop teachers. He then traces the historical roots of these ideas to propose critically why the research movement withered. The overall aim of the book is to introduce some alternative theoretical foundations and propositions for the sake of innovative discussions about teachers' continuing educational development.